1. Respiration
Chapter 24

2. Types of Respiratory Systems
Respiration is the uptake of oxygen and the simultaneous release of carbon dioxide.
Most primitive animal phyla obtain oxygen directly from their environments through diffusion.
More advanced phyla have specific respiratory organs:
Gills, tracheae, and lungs

3. Gas exchange in animals
CO2 O2
Gill filament
CO2
Body wall O2
Gill
Fish
Blood vessels
Flatworm
Tracheoles
Trachea O2
Trachea
Mammalian lung
Blood vessels
Alveoli
Mammal
CO2 O2
Spiracles
CO2 O2
CO2
Spiracle
Terrestrial arthropod

4. Respiration in Aquatic Vertebrates
Water always moves past a fish’s gills in one direction.
Gill raker
Gill arch
Water
Gill filaments
Lamellae with
capillary networks
Direction of water flow
Direction of blood flow
Vein
Artery

5. Respiration in Aquatic Vertebrates
Blood (85%
O2 saturation)
Countercurrent exchange
Concurrent exchange
Water (50%
Water (100%
O2saturation)
Blood (50%
No further
net diffusion
50%
60%
70%
80%
90%
(b)
Blood (0%
Water(15%
10%
20%
30%
40%
85%
100%
15%
(a)
Water(100%
Moving the water past the gills in the same direction permits countercurrent flow.
This process is an extremely efficient way of extracting oxygen.
Blood flows through a gill filament in an opposite direction to the movement of water.
The blood in the blood vessels always encounters water with a higher oxygen concentration, resulting in the diffusion of oxygen into the blood vessels.

6. Respiration in Terrestrial Vertebrates
Lungs are less efficient than gills because new air that is inhaled mixes with old air already in the lung.
But there is so much more oxygen in air than in water.

7. Respiration in Terrestrial Vertebrates
The lungs of mammals possess on their inner surface many small chambers called alveoli, which greatly increases surface area for the diffusion of oxygen.
(a) Amphibian
(b )Reptile
(c) Mammal
Alveoli
Bronchiole

8. Respiration in Terrestrial Vertebrates
Flying creates a respiratory demand for oxygen that exceeds the capacity of the saclike lungs of even the most active mammal.
Birds have evolved the most efficient lung.
An avian lung is connected to a series of air sacs outside of the lung.
Lung
Trachea
Anterior
air sacs
(a)
Posterior
(b)
Inspiration
Parabronchi of lung
Expiration
Cycle 1
Cycle 2

9. Respiration in Terrestrial Vertebrates
This creates a unidirectional flow of air through the lungs.
Blood flow and airflow are not opposite but flow at perpendicular angles in crosscurrent flow.
Avian lungs
Mammalian lungs
Uniform pool
Cross current
Counter current
Fish gills
Blood
(c)

10. The Mammalian Respiratory System
Nasal cavity
Nostril
Glottis
Larynx
Trachea
Right lung
Pharynx
Epiglottis
Left lung
Left
bronchus
In the mammalian respiratory system, air passes in and out of the lungs, which are housed in the thoracic cavity.
Air is warmed and filtered as it flows through the nasal cavity.
It passes next through the pharynx, then the larynx (or voice box), then to the trachea, or windpipe.

11. The Mammalian Respiratory System
From there, air passes through several branchings of bronchi in the lungs and then to the bronchioles.
The tissue of the lungs is divided into tiny air sacs called alveoli; through these thin-walled cells, gas exchange with the blood occurs.
Blood flow
Smooth muscle
Bronchiole
Pulmonary arteriole
Pulmonary venule
Alveolar
sac
Alveoli
Capillary network
on surface
of alveolus

12. The Mammalian Respiratory System
The mammal respiratory apparatus is simple in structure and functions as a one-cycle pump.
A diaphragm muscle separates the thoracic cavity from the abdominal cavity.
Each lung is covered by a thin, smooth membrane called the pleural membrane.
This membrane adheres to another pleural membrane lining the walls of the thoracic cavity, basically coupling the lungs to the thoracic cavity.

13. The Mammalian Respiratory System
Air is drawn into the lungs by the creation of negative pressure.
The active pumping of air in and out is called breathing.
During inhalation, muscular contraction causes the chest cavity to expand.
During exhalation, the ribs and diaphragm return to their original position.

14. Key Biological Process: Breathing1 2 3
Pair
Pair
Pair
Inhalation
Exhalation
Chest
cavity
expands
Plung
Plung
Plung
Diaphragm
relaxed
Diaphragm
relaxed
Diaphragm
contracts
Plung
>
Pair
Plung = Pair
Plung
<
Pair
Before inhalation, the air pressure in the
lungs (Plung) is equal to the atmospheric
pressure (Pair).
During inhalation, the diaphragm
contracts, and the chest cavity expands
downward and outward. This increases
the volume of the chest cavity and lungs,
which reduces the air pressure inside the
lungs, and the air from outside the body
flows into the lungs.
During exhalation, the diaphragm relaxes,
decreasing the volume of the chest
cavity. The pressure increases in the
lungs, forcing air out of the lungs.

15. How Respiration Works: Gas Exchange
Oxygen moves through the circulatory system carried by the protein hemoglobin.
Hemoglobin molecules contain iron, which binds oxygen in a reversible way.
Heme group
Beta (β) chains
Oxygen (O2)
Iron (Fe++)
Alpha () chains

16. How Respiration Works: Gas Exchange
Hemoglobin molecules act like little sponges for oxygen.
At the high O2 levels that occur in the blood supply at the lung, most hemoglobin molecules carry a full load of O2.
In the tissues, the O2 levels are much lower, so hemoglobin gives up its bound oxygen.
In the presence of CO2, the hemoglobin assumes a different shape that gives up its oxygen more readily.

17. How Respiration Works: Gas Exchange
CO2 must also be transported by the blood.
About 8% simply dissolves in the plasma.
20% is bound to hemoglobin but at a different site than where O2 binds.
The remaining 72% diffuses into the red blood cells.
In order to maintain the gradient for CO2 to leave the tissues and enter the plasma, the CO2 levels in the plasma must be kept low.

18. How Respiration Works: Gas Exchange
The enzyme carbonic anhydrase combines CO2 with water to form carbonic acid (H2CO3).
This acid dissociates into bicarbonate (HCO3–) and H+.
Bicarbonate also acts as buffer in the blood plasma.
In the lungs, the reverse reaction takes place, and CO2 is released.

19. The Nature of Lung Cancer
Lung cancer is one of the leading causes of death among adults.
Mutations to two tumor-suppressing genes are implicated in the development of cancer.
Rb codes for Rb protein, which acts as a brake on cell division.
p53 codes for p53 protein, which detects damaged or foreign DNA and prevents its replication.

20. The Nature of Lung Cancer
Smoking causes lung cancer.
The annual incidence of lung cancer is much higher for smokers than for nonsmokers.
Changes in the incidence of lung cancer have mirrored changes in smoking habits.
Many types of mutagens are found in cigarette smoke that can damage genes.
The p53 gene is damaged in 70% of lung cancers.
Smoking also leads to nicotine addiction.

21. Incidence of lung cancer in men and women1
Per capita cigarette consumption
Lung cancer death rates per 100,000
3000
2500
2000
1500
1000
500
1900 10 20 30 40 50 60 70 80 90
Males
Cigarette
consumption
30years
Lung
cancer
deaths
Time
Females
100
2010
1910
1920
1930
1940
1950
1960
1970
1980
1990
960
Incidence of lung cancer in men and women